Concrete reservoir for underwater use

ABSTRACT

A reservoir of prestressed reinforced concrete preferably for storing hydrocarbons, adapted so that it can be submerged in the sea so that it rests freely on the bottom thereof, said reservoir comprising a series of cylindrical walls into which radiating partitions fit so that they bear on a central pillar formed by two circular slabs fitting into the walls and the partitions. The bottom of the reservoir has a reinforcement designed to receive a supporting pad or cushion, and the top of the reservoir carries at least one columnar support having a working platform at its upper end. This platform remains above the surface of the sea after the reservoir has been submerged. Each support is in the form of a hollow shaft and serves to carry means connecting the tank with safety elements on the work platform. Further, each shaft is provided with first means which allow the tank to be submerged in the sea so that it can rest freely on the bottom thereof and second means which allow the tank to &#39;&#39;&#39;&#39;breath&#39;&#39;&#39;&#39; by enabling the safety elements to be brought into communication with the free atmosphere. Preferably each shaft has a number of cells therein which can be successively flooded with sea water to lower the reservoir to the sea bottom in stages and desirably the reservoir is made from prestressed reinforced concrete.

United States Patent Roulet et al. [451 Jan. 9, 1973 [54] CONCRETE RESERVOIR FOR Primary Examiner-J. Karl Bell UNDERWATER USE Attorney-Holcombe, Wetherill & Brisebois [76] Inventors: Jean Roulet, 6, Hameau Les Pin- [57] ABSTRACT sons La Cene Sam'CIOud; A I reservoir of prestressed reinforced concrete f 10 rue Edouard preferably for storing hydrocarbons, adapted so that it Mortler Nemny both of France can be submerged in the sea so that it rests freely on r the bottom thereof, said reservoir comprising a series [22] Filed: July 23, 1971 of c lindrical walls into which radiatin artitions fit y g P so that they bear on a central pillar formed by two cir- [21] Appl. No: 165 060 cular slabs fitting into the walls and the partitions. The bottom of the reservoir has a reinforcement designed to receive a supporting pad or cushion, and the top of Related U-S- Application Data the reservoir carries at least one columnar support [63] Continuation-impart of Ser. Nos. 884 584 Dec. l2, having a working platform at its upper This plat- 1969 abandoned and 8 23 form remains above the surface of the sea after the 1969 abandoned reservoir has been submerged. Each support is in the form of a hollow shaft and serves to carry means con- [52] US. Cl ..6l/46 i the tank with Safety elements the Work 51 Int. Cl. ..E02d 27/38 platfmm- Further 6811 Shaft is Pwvided with first [58] Field of Search 61/5 46 52/223 means which allow the tank to be submerged in the 5 5 sea so that it can rest freely on the bottom thereof and second means which allow the tank to breath by [56] References cued enabling the safety elements to be brought into communication with the free atmosphere. UNITED STATES PATENTS Preferably each shaft has a number of cells therein 2,204,955 6/1940 Beeby ..52/296 hich can be successively flooded with sea water to 2,687,017 8/1954 Gerwick ..6l/46 lower the reservoir tothe sea bottom in stages and 3,091,089 5/1963 Gellerstad i ..6i/46 desirably the reservoir is made from prestressed rein- 3,l46,458 8/1964 Estes et al. .....6l/46.5 forced concrete, 3,472,033 10/1969 Brown 61/465 X 3,501,920 3/1970 Uchiyama ..52/223 10 Claims, 13 Drawing Figures O O 4 o o Ill III] I n \l I ,i I o I SHEET 2 OF 7 PATENTEDJAN 9 I973 I I I I I I I I I I I I I all/f AJJIE I'll PATENTEDJAM 9I973 310mm saw 8 OF 7 Fig.

PATENTEDJAN 9 I973 SHEET 7 BF 7 to E 1 ll AV 1 CONCRETE RESERVOIR FOR UNDERWATER USE This application is a continuation-in-part of my prior applications Ser. No. 884,584, filed Dec. 12, 1969, and

Ser. No. 887,626, filed Dec. 23, 1969, both now abandoned.

SUMMARY OF THE INVENTION The present invention relates to reservoirs of large capacity, made of prestressed reinforced concrete which are adapted to be submerged in a fluid.

The reservoirs used on land for storing hydrocarbons have various disadvantages. In particular, they have to be installed close to port areas and this restriction becomes serious in the production zones and particularly in off-shore production zones.

Floating reservoirs have been proposed but this technique has various disadvantages, particularly with respect to the stability of the reservoir.

Reservoirs for submersion have recently been constructed, but so far their construction has encountered difficulties, due to the effects of the ocean swell at the depth of the reservoir. Actually, alternating forces are added to the forces created by the difference in density between the stored fluids andthe surrounding water.

In order to overcome these forces, which tend to displace or upset the reservoir, it is necessary to hold the latter in a stationary position by means of anchoring devices, which are difficult to provide. Furthermore, the holding force of these anchoring systems in time becomes uncertain.

One of the objects of the present invention is to provide an unanchored reservoir adapted to be submerged in a fluid.

Another object of the present invention is to provide a reservoir directly positioned on the sea bottom which resists movement in response to the stresses to which it is subjected as a result of its inherent characteristics.

Another object of the present invention is to provide a com'partmen'ted reservoir which is adapted to be placed on the sea bottom and ofwhich has a stabilized sea water-hydrocarbon interface. Another object of the present invention is to provide a reservoir adapted to be positioned on the sea bottom, in which the stress resulting from the support of the reservoir on the sea bottom is smaller than the stress necessary to cause a noticeable deformation of the sea bottom.

Another object of the present inventionis to provide a large capacityreservoir which can be immersed in position on the sea bed after having been constructed on land.

Another object of the present invention is to provide a reservoir which can be positioned on the sea bottom, in which the deposit of paraffin which may be produced on the walls of the reservoir does not interfere to any substantial degree with the various operations of storage, filling and emptying.

Another object of the present invention is to provide a reservoir in which the stored hydrocarbons are in contact with the sea water.

Another object of the present invention is to provide a reservoir in which the movements of the sea water in contact with the hydrocarbons inside the reservoir are inhibited by means of a series of openings of small diameter situated on the one hand in the ring on which the reservoir is resting and on the base of the reservoir.

As is well known, a reservoir for crude petroleum, especially when it is of large capacity, has to be equipped with a certain number of elements for the treatment of the stored crude oil and as safety elements for maintaining a pressure in the reservoir which is below the admissible excess pressure, this pressure varying with the stored crude oil and the temperature, and being due to the volatilityphenomena of the light constituents of the crude oil. 1

In the case of immersed reservoirs, the safety elements have to open into the outside atmosphere so as to ensure that the reservoir can breath.

The invention accordingly provides a reservoir with means capable of permitting the safety elements of the reservoir to be brought into communication'with the outside atmosphere when it is immersed, and further a reservoir with means capable of receiving accessible installations for the extraction of gas and paraffin from the hydrocarbons stored in the reservoir.

According to the invention therefore a concrete reservoir which is adapted to be immersed in the sea so that it rests freely on the bottom thereof comprises a plurality of cylindrical walls of equal height arranged concentrically about a vertical axis, said walls being interconnected by upright radial partitions of the same height as said walls and second partition members defining compartments, said first partitions being apertured partitions in which said apertures may be closed,

other hand in the and the said reservoir having a top and bottom which fit into the said cylindrical walls and the said vertical'partitions, said bottom having a supporting ring'thereon and said topbeing adapted to receive connection means for filling and emptying the reservoir. I

According to one feature of the invention, the reservoir is made of prestressed reinforced concrete and each wall is two-dimensionally prestressed, so that if the reservoir is subjected to a vertical lifting force because of the difference in density between the fluids in the said reservoir and the surrounding sea water or due to the swell of the sea, the reservoir has sufficient support to ensure stability. Each of the walls of said compartments has an upper and lower part which is apertured so that each compartment communicates with the adjacent compartments so as to stabilizefthe reservoir and oppose the establishment of an upsetting torque.

In one constructional form, an annular ring is formed on the bottom and adapted to receive an annular cushion pad for ensuring the continuous support of the said reservoir on the sea bottom.

In another embodiment, the reservoir comprises three supporting zones spaced at and integrated into the bottom, which is reinforced in the region of each supporting zone.

In one preferred embodiment, the walls and the partitions of the reservoir are two-dimensionally prestressed in two substantially perpendicular directions, whereas the tip and bottom are two-dimensionally prestressed along three directions inclined at 120 to each other, thus three-dimensionally prestressing the structure, which ensures a cohesion of the construction over a period of time.

The compartments formed by the multiple partitions and the-annuli formed by the multiple rings ensure,

because of theirinherent rigidity, a complete structural I indeformability under all the stresses which are applied.

The reservoir can also be given an internal or external lining made of metal or synthetic resins of the epoxy type or a mixtureof pitch and epoxy resin, which 'ensures perfect fluid-tightness.

The reservoir is provided with a cover which is equipped with at least one support on which is fixed a working platform, each support being constructed in the form of a hollow shaft, each of which receives housing means connecting the reservoir with safety elements located in the vicinity of said platform, the shaft or shaftsbeing provided with first means which allow the reservoir-to be submerged in the sea so that it rests freely on the bottom thereof and second means which allow the reservoir to breath by allowing the safety elements to be brought into communication with the free atmosphere.

According to one feature of the invention, the base of the or each shaft is embedded in the cover slab of the reservoir. I

According to another feature of the invention, the or each shaft is made of three-dimensionally prestressed reinforced concrete. a

. Ina preferredconstruction, the or each shaft is' in the form of a volume of revolution, formed by an annular cylinder, of which the wall has a trapezoidal section,

the circular section being prestressed circularlyand the generatrix receiving a longitudinal prestressing.

According to one feature of the invention, each shaft made of prestressed reinforced concrete receives a three-dimensional prestressing applied by means of cables'or rods which are embedded in the partitions or the walls forming the compartments of the reservoir, the said partitions or walls'beingthemselves prestressed two-dimensionally;

drawings,in which: a

FIG. 1' is a horizontal sectional view of a reservoir having two cylindrical walls. I

FIG..2 is-a vertical sectional view of the same reser voir, havingjasmooth bottomresting on the seabed.-

FIG. 3 is a "vertical sectional viewofa similar're servoir, including a ring which supports the reservoir on a smooth sea bed. 1 F

- FIG. 4 is a vertical'sectional view of a reservoir resting on a rocky bott'om. i a

FIG. 5 is a top plan view of a reservoir having three cylindricahwalls. y l 1 FIG. 6 is a sectional view of the same reservoir supported on a sandy. bottom by a supporting ring.

FIG. 7 shows. diagrammatically the constructional features common to the top and bottom of the reservoir, which are under two-dimensional stress.

FIG. 8 is a detail view showing the junction between the cover ortop'of the reservoir and its external wall.

FIG. 9 is adetail view showing the junction between two cylindrical walls 'and'a vertical partition,

FIG. 10 isa vertical sectional view taken through a reservoir equippedwith a single shaft, I

FIG. 11. is a' vertical sectional view taken through a reservoir having three shafts,

ample only,' with reference to, the accompanying I The invention will now be described, by way, of ex- FIG. '12 is a vertical sectional view taken through a reservoir having a shaft provided with means whereby the reservoir can be immersed in the sea in stages, and

FIG; 13 is a vertical sectional view taken through a reservoir with a shaft equipped with an immersion device which can be moved during the immersing operation. a

FIG. 1 shows a reservoir according to the invention.

having a cylindrical wall 1 made of reinforced concrete, prestressed in two dimensions and surr0unding the reservoir. Inside the wall v1 is a second cylindri cal wall 2, constructed in the same way asthe wall 1. A

are all of relatively small dimensions, provide commu-v nication between both the-upper andlower parts of the different compartments, andmay be provided with closure means. A series of holes 10 formedin the floor .or bottom surface of the reservoir enable the lower part of the central compartment to communicate with the surrounding medium, that is to say, with the sea-water, when the reservoir is supported above the ocean floor as shown in FIG. 3. i

FIG.2 shows the reservoir of FIG. 1 in vertical section, and resting on a sea bottom or ground'which is unstable.-Whe n the reservoir is placed in position, it sinks into the ground. The reservoir com-prises cylindrical walls v1 and 2, and a common axis 8 of the cylinders at which the different partitions meet. A cover or top 11 and a floor or base 12in which holes were provided-in communication with the (sea floor 10 are shown. Openings 13 formed at'the' bottomofthe central compartment bring thelatter intocommunieation with the exterior by way of chimneys which are provided for example, in the walls er in th e'central compartment. FIG. 2 shows a series fppe nings 14 whichare" situated in the'upper part of the-partitions, permitting the circulation of the petrol stored injthe reservoir between adjacent compartments. Finally; FIG. 2:.show's at 16 the union which ensures the connection between the different compartments and the emptying and'filling conduits.

FIG. 3 shows the reservoir of l,.supported on a stable sea bottom. Thisis .foriex'ample the case with a sandy bottom, where the surface .is either flat or undulisting. The upper part of the reservoir'isidentical with the part of the reservoir which is described in connection with FIG.'-2. The floor however comprises a reinforcement 17 in the form of anannular-ring, the lower' is formed with a number of openings of small diameter which allow the sea water to circulate thereby ensuring the stability of the interface between the water and the oil.

FIG. 4 shows the reservoir of FIG. 1, resting on a rocky sea floor on multiple supports.

The reservoir is very similar to that just described, but includes three supporting pads 20, 21, 22 resting as three points on the sea floor, the supporting pads shown being of identical height.

FIG. 5 illustrates a reservoir having three cylindrical walls, the storage capacity of this reservoir being greater than that of FIG. 1. By way of example, the reservoir FIG. 1 can hold approximately 40,000 cubic meters of hydrocarbon, whereas the reservoir of FIG. 5 can hold more than 70,000 cubic meters. By adding successive rings, it is possible to increase the capacity of the reservoirs and thereby obtain reservoirs of very large capacity. Conversely, the reservoirs with a single cylindrical wall permit much smaller capacities to be held.

The three cylindrical walls 23, 24 and 25 by whic the reservoir is subdivided into vertical compartments are shown. These cylindrical walls are made of prestressed reinforced concrete which are subjected to a series of horizontal stresses and to a series of vertical stresses. Three partitions 26, 27 and 28 lie at an angle of 60 relative to one another, and are fitted in the three cylindrical walls 23, 24 and 25 and the axis 29 common to these three cylinders. Partitions 30, which are connected only to. the three cylindrical walls 23, 24 and 25, provide compartments subtending an angle of 30. Two series of openings 31, one series being positioned at the base of the partitions and the other at the top of the said partitions are also provided together with six orifices 31a formed in the floor of the'reser- VOII'.

FIG. 6 shows the reservoir of FIG. 5 in vertical section, when it is resting on a sandy sea floor 34. The cylindrical walls 23, 24 and 25 are shown, and also the 35 of the-floor. This-reinforcement carries a cushion or pad 36 which contacts the sea bottom, supports the tank andprovides insulation between the base of the reservoir and the sea bottom. .Two series of openings 37 and 38 are also provided and the holes 31 in the base can beseen.

FIG 7 illustratesthe method of assembly of both the floor and the cover. The six circular sectors 39, 40, 41, 42, 43 and 44 forming the compartment sections situated between any two adjacent partitions are shown, these sectors being successively cast on a grid consisting of three groups of wires serving to prestress the structure and form between them angles of 120. Recesses 45, 46 and 47 are formed in the floor or the cover and these'recesses, once the different circular sections have been cast, permit the partial setting and shrinkageof the concrete before keying and the application of the prestressing elements. The latter are subjected, by means of grids 48, 49 and 50, to a twodimensional prestressing sufficient to'give the desired resistance to the concrete.

The prestressing cables are embedded in the concrete mass and covers therefor are injected after they have been placed under tension so that these cables are very efficiently protected.

y the reservoir.

The cylindrical walls are likewise formed with twodimensional prestressing. The partitions are also made of two-dimensional prestressed reinforced concrete, so that the reservoir assembly as a whole is a three-dimensionally prestressed structure.

FIG. 8 shows a junction between a vertical cylindrical wall and the covering slab. Shown at 51 is one of the prestressing cables which enables a two-dimensional stress to be established in the cover slab by means of three groups of cables disposed at 120, as explained in connection with FIG. 7. The other cable groups are shown in section at 52 and 53 The cover slab 54 has a reinforcement 55, which serves to sealingly cover the head 56 of the prestressing cable 57,'thereby ensuring that there is a vertical stressing along an internal generatrix of the vertical wall. Three cables 58, 59 and 60 are i also shown which ensure a horizontal prestressing of the vertical wall 61. The whole exterior surface of the reservoir is covered with a layer of epoxy resin,62, which permits the fluid-tightness to be improved over that already provided by the prestressing of the concrete.

FIG. 9 shows in plan a junction between the vertical walls and a vertical partition including an external wall 62, an internal wall 63, a connecting partition 64 and the cables 65 and 66 by which the cylindrical wall can be subjected to a horizontal stress, the cable sections 67, 68, 69 and 70 ensuring a vertical prestressing. A .cable 71 is also embedded in'the wall 62 and places the partition 64 under horizontal prestress. Cables 72,73, 74, 75, 76, 77 and 78 ensure the prestressing in the perpendicular direction i.e., in the vertical direction;

Two cables 79 and 80 ensure a horizontal prestressing in the cylindrical wall 63, the vertical prestressing being assured by cables 81, 8 2, 83, 84, and 8 6. t

It is thus seen that the reservoir is in fact-given a three-dimensional prestressing by, the action of the fittings. i

From the top of the reservoirthere extends'a vertical shaft 88 which is cylindrical in shape. It is to be pointed out that the sections shown in FIGS. 10-13 are taken in a plane containing the partitions forming the compartments in the reservoir. These partitions contain horizontal prestressing" cables 71 and the vertical prestressingcables72, 73 as previously described. Positioned in the walls of the shaft are prestressing cables1l5 and 116, which splay out in the partition, thus anchoring the shaft in thepartitionand in the floor of At the top of the shaft, and abovethe surface of the sea, is a working platform 18. Inside the hollow shaft 88 is a control unit 88a, which is directly accessible from the working platform by descending into the interior of the shaft, and to this control unit the different conduits 19a and 1% used during operation of the reservoir are connected. A ring valve 20. permits the volatile products to .be discharged into the atmosphere when a certain pressure is exceeded. Furthermore, a connection 21 is connected to a float 22, which may be connected to a tanker ship for discharging the stored crude oil by means of a pipe 23.

In FIG. 11, the central pillar and the vertical walls of the reservoir are better shown. A cover slab on this reservoir is fixed in the same manner as indicated in FIG. 10'and three shafts 126, 127 and l28are fixed on the reservoir and are mounted in the same manner as the shaft 88 of FIG. 10-, and are, inparticular, anchored by prestressing in the partitionsand walls .of the reservoir;

' Above the sea level 121, a platform 129 covers these three shafts, which are spaced at 120 relatively to one 'another and thus permit a platform of large area to be 135b from which a flexible pipe 1350 can be connected to a tanker ship, with the object of discharging the stored crude oil.

FIG. 12 shows a reservoir having a single shaft, and illustrates how the reservoir is submerged in the sea. The reservoir, already constructed beforehand on land, is towed to the place where it is to be submerged, in a semi-immersed.position, that is to say, with the cover slab of the reservoir slightly below the water to a depth of the order of -a few meters. The major portion of the shaft thus extends above the surface of the sea. The reservoir itself is'partially filled ,with water. The shaft 137, on the other hand,.is empty, thus'giving the assembly a slight'positive floatability.

. inorder to submerge the reservoir, which process has to be carriedout while maintaining a small pressure differential between-the interior and exterior (this differentialwpres'sure being determined by the characteristics of the reservoir), the reservoir is submerged in stages, that is to say, the reservoir is lowered to itsfinal submerged position in stages of about 10 meters. For this purpose, a series of partitions 138, 139, 140, 141,

142, spaced apart by a height of about 10 meters, are

arranged in the shaft 137. These partitions are provided with valves, which allow a certain quantity of seawater to enter the shaft. As a result, thebuoyancy of the assembly is-adjusted sothat the reservoir is progressively reservoir. and lower it with given force onto-the sea bottom. The platform 43 then stands above the level of the sea.

FIG. 13- shows a different embodiment of. the shaft shown in FIG. 12. This shaft includes a series of-partitions 145, 146, .147. and l48at the top of which is positioned a valve 149 connected by a flexible .pipeto the base of the shaft. A certain volume of water can therefore .be injected at each stage of submersion into the shaft so as to cause the reservoir to descend by a predetermined amount. At the same time, a predetermined quantity of air is injected into the reservoir, so that his subjected to a differential pressure less than the admissible limiting pressure. Once the reservoir is inposition, the platform l50 stands above sea level and serves to receive the various pieces of necessary ancillary equipment. 7

An alternative method of submersion is to allow sea water to flow into the shaft at a controlled rate of flow,- while simultaneously regulating the air pressure in the reservoir. r

After the reservoir has been-immersed, it is positioned on the sea bottom in accordance with various procedures which depend on the nature of the bottom.

The connection between the control unit carried by the upper covering slab and the pipes serving for the working of the. reservoir is now made. It is thus possible to inject into the reservoir chambers hydrocarbons which force the sea water ahead of them. The injection is then made under pressure and continued until a sufficient volume of hydrocarbons fills the reservoir almost to its full capacity but stops short of the top of the reservoir by a distance of 1 meter for example thereby leaving a water trap. I

The hydrocarbons can be withdrawn from the reser- 5 voir either by allowing the oil to flow because of the pressure applied by the sea water, or by creating a vacuum by pumping. The water-oil interface is stabilized, both for'the movements created during a filling or emptying operation or during movements due to the swell and the currents of the sea. It can be established that there is an attenuation'and a shift in phase of the interface movements relatively to the movements imposed by the sea, particularly the swell. These attenuations and shifts in phase are created by the size of the orifices through which the sea and the contents of the reservoir are brought into communication. This reservoir never lifts from the bottom, because its own weight is considerably greater than the force created by the differencein density'between the hydrocarbons-and the sea water and the vertical forcesv due tothe swell. The apparent weight of the reservoir completely filled with hydrocarbon is sufficient to ensure a downward pressure by the reservoir" on the sea bottom which opposes the lifting and slipping of the said reservoir.

What is claimed is:

l. A concrete reservoir for hydrocarbons adapted to rest unanchored on the bottom of a body of water, said reservoir-comprising in combination a plurality of vertical walls, a floor and a cover defining a plurality of adjacentcompartments, each of said walls, floor and cover being made of concrete prestressed in two directions,- I I atleast some of'said compartmentsibeingformed with a first group of apertures in their lower parts leading to the exterior of the reservoir for admitting ambient water tov the bottom of said compartments, and at least some of said'eompartments being formed with a second group of apertures in their upper parts connecting adjacent compartmentsso that hydrocarbons stored-in said compartmentsabove said water may flow back and forth there between, 1

a hollow shaft integrally connectedto said cover and dimensioned to project above 'water when said reservoir is on the bottom of said body of water, and

conduit means extending through said shaft into said reservoir for introducing fluids into said reservoir through said shaft and for withdrawing fluids therefrom.

2. A concrete reservoir as claimed in claim 1 comprising means for opening and closing said apertures.

3. A concrete reservoir as claimed in claim 1 in which said shaft is made of concrete and prestressed by means of cables extending into at least some of said reservoir walls.

' 4. A concrete reservoir as claimed in claim 3 in which said reservoir walls comprise partitions radiating from the longitudinal axis of said shaft and the lower ends of the cables prestressing said shaft splay radially outward in said partitions.

5. A concrete reservoir as claimed in claim 1 in which said shaft is divided into a plurality of superposed compartments by transverse partitions, said transverse partitions being provided with valved apertures which permit a selected liquid to be introduced into any desired number of said superposed compartments so as to regulate the buoyancy of the reservoir.

6. A concrete reservoir as claimed in claim 5 comprising means for introducing air into said superposed compartments.

7. A concrete reservoir as claimed in claim 1 comprising a plurality of cylindrical walls arranged concentrically about a vertical axis and interconnected by vertical radial partitions to define said compartments.

8. A concrete reservoir as claimed in claim 7 in which said floor comprises an external supporting ring which holds an annular cushion supporting said reservoir.

9. A concrete reservoir as claimed in claim 7 comprising three supporting members spaced at 120 from each other and integrated into said floor, which is reinforced adjacent each supporting memberr 10. A concrete reservoir as claimed in claim 1 which is lined with a material selected from the group consisting of metals, synthetic resins, and a combination of pitch and epoxy resins.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,7 ,9 7 Da e 9 January 1973 Invent0r(s) JEAN ROULET and ARMAND CIMADEVILLA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data December 26, 1968 France .l80,597

Signed and sealed this 6th day of August 197 (SEAL) Attest:

MCCOY Ma GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents uscoMM-Dc 60376-P69 US GOVERNMENT FRINTING OFFICE I969 O366-334,

FORM PO-105O (10-69) 

1. A concrete reservoir for hydrocarbons adapted to rest unanchored on the bottom of a body of water, said reservoir comprising in combination a plurality of vertical walls, a floor and a cover defining a plurality of adjacent compartments, each of said walls, floor and cover being made of concrete prestressed in two directions, at least some of said compartments being formed with a first group of apertures in their lower parts leading to the exterior of the reservoir for admitting ambient water to the bottom of said compartments, and at least some of said compartments being formed with a second group of apertures in their upper parts connecting adjacent compartments so that hydrocarbons stored in said compartments above said water may flow back and forth there between, a hollow shaft integrally connected to said cover and dimensioned to project above water when said reservoir is on the bottom of said body of water, and conduit means extending through said shaft Into said reservoir for introducing fluids into said reservoir through said shaft and for withdrawing fluids therefrom.
 2. A concrete reservoir as claimed in claim 1 comprising means for opening and closing said apertures.
 3. A concrete reservoir as claimed in claim 1 in which said shaft is made of concrete and prestressed by means of cables extending into at least some of said reservoir walls.
 4. A concrete reservoir as claimed in claim 3 in which said reservoir walls comprise partitions radiating from the longitudinal axis of said shaft and the lower ends of the cables prestressing said shaft splay radially outward in said partitions.
 5. A concrete reservoir as claimed in claim 1 in which said shaft is divided into a plurality of superposed compartments by transverse partitions, said transverse partitions being provided with valved apertures which permit a selected liquid to be introduced into any desired number of said superposed compartments so as to regulate the buoyancy of the reservoir.
 6. A concrete reservoir as claimed in claim 5 comprising means for introducing air into said superposed compartments.
 7. A concrete reservoir as claimed in claim 1 comprising a plurality of cylindrical walls arranged concentrically about a vertical axis and interconnected by vertical radial partitions to define said compartments.
 8. A concrete reservoir as claimed in claim 7 in which said floor comprises an external supporting ring which holds an annular cushion supporting said reservoir.
 9. A concrete reservoir as claimed in claim 7 comprising three supporting members spaced at 120* from each other and integrated into said floor, which is reinforced adjacent each supporting member.
 10. A concrete reservoir as claimed in claim 1 which is lined with a material selected from the group consisting of metals, synthetic resins, and a combination of pitch and epoxy resins. 